BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to an ink-jet printing head, more particularly relates
to a method of producing a flow passage forming substrate.
2. Description of the Related Art
[0002] In an ink-jet printing head, as shown in Fig. 13, a flow passage unit is constituted
by a flow passage forming substrate F in which a reservoir A to which ink is supplied
from an outside tank, a pressure generating chamber B which is concave and pressurized
from the outside, an ink supply port C connecting the reservoir A and the pressure
generating chamber B and a nozzle communicating hole E which is a through hole and
connects the pressure generating chamber B and a nozzle aperture D are formed, an
elastic plate G for sealing one surface of the flow passage forming substrate F and
a nozzle plate H provided with the nozzle aperture D for sealing the other surface
of the flow passage forming substrate F. The ink-jet printing head is constituted
so that ink in the reservoir A is sucked in the pressure generating chamber B via
the ink supply port C by touching a piezoelectric vibrator J to the elastic plate
G and expanding the pressure generating chamber B by the displacement of the piezoelectric
vibrator J and an ink droplet ejects from the nozzle aperture D by pressurizing ink
the pressure generating chamber B by contracting the pressure generating chamber B.
[0003] As in such an ink-jet printing head, full color printing can be readily executed
by using color ink, the ink-jet printing head is rapidly popularized as a printing
head of a color printer and hereby, it is demanded that printing quality and density
are further enhanced.
[0004] As the printing quality and density of an ink-jet printing head greatly depend upon
the size of a dot which an ink droplet forms, it is required to reduce the quantity
of ink per droplet as much as possible to miniaturize the size of a dot.
[0005] Therefore, the volume of a pressure generating chamber can be reduced as much as
possible and, in addition, pressure generating chambers can be arrayed in high density
by arraying pressure generating chambers in high density, selecting a substrate 300
µm or more thick, desirably a substrate approximately 500 µm thick, for example a
monocrystalline silicon substrate in view of working precision as a flow passage forming
substrate in consideration of preventing a flow passage forming substrate from being
deformed by pressure when an ink droplet ejects and, further, facility in handling
in assembly and forming the pressure generating chamber as a shallow concave portion
by photolithography and anisotropic etching as disclosed in Unexamined Japanese Patent
Application No. Sho. 58-40509.
[0006] When the pressure generating chamber is constituted on one surface of the substrate
as a concave portion as described above, the nozzle communicating hole E for connecting
the pressure generating chamber and the nozzle aperture is required to let the pressure
generating chamber communicate with the nozzle aperture D of the nozzle plate arranged
on the surface on the side reverse to the surface on which the pressure generating
chamber is formed.
[0007] Such a nozzle communicating hole E is formed by making a through hole with a minute
diameter pierced from one surface to the other surface in an area to be the nozzle
communicating hole E beforehand as disclosed in Unexamined Japanese Patent Application
No. Sho. 5-309835 and executing anisotropic etching to the depth using the above through
hole as an etching pilot hole so that the width of the nozzle communicating hole E
is approximately equal to the width of the pressure generating chamber B at the maximum.
[0008] Therefore, as shown in Fig. 14, as the height of a partition in an area K' which
faces the nozzle communicating hole E is equal to the thickness d' of the monocrystalline
silicon substrate and large though the partition in the vicinity of the pressure generating
chamber is provided with high rigidity because the depth d of the pressure generating
chamber B is small in an area K in the vicinity of the pressure generating chamber
of partitions for partitioning the pressure generating chambers B, the rigidity of
the partition between the adjacent nozzle communicating holes E is extremely small
and there is a problem that pressure when ink is jetted elastically deforms the area
K' and crosstalk is caused between the adjacent pressure generating chambers B.
SUMMARY OF THE INVENTION
[0009] An ink-jet printing head according to the present invention is provided with a flow
passage forming substrate in which a pressure generating chamber, a reservoir, an
ink supply port and a nozzle communicating hole which is a through hole are formed,
a nozzle plate provided with a nozzle communicating with the pressure generating chamber
via the nozzle communicating hole, a capping member for sealing the side of the pressure
generating chamber of the flow passage forming substrate and pressure generating means
for pressurizing the pressure generating chamber, two reservoirs are formed with the
pressure generating chamber held between the two reservoirs, the pressure generating
chamber communicates with at least one reservoir of them via the ink supply port,
and the nozzle communicating holes are arranged zigzag in an approximately symmetrical
position in which the center in the longitudinal direction of the pressure generating
chamber is held between the adjacent nozzle communicating holes and so that one of
the adjacent nozzle communicating holes is shifted in the longitudinal direction of
the pressure generating chamber.
[0010] Hereby, as the height of a partition for partitioning the nozzle communicating hole
which is a through hole and the adjacent pressure generating chamber is approximately
equal to the height of a partition between the pressure generating chambers, the flow
passage forming substrate can be provided with sufficient rigidity. Therefore, even
if the pressure generating chambers are arrayed in high density, a piezoelectric vibrator
smaller than the outside diameters of a diaphragm may be used and crosstalk can be
prevented.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
Figs. 1 (a) and 1 (b) show an embodiment of an ink-jet printing head according to
the present invention as the sectional structure viewed along a center line between
adjacent pressure generating chambers, Fig. 2 is a top view showing an embodiment
of a flow passage forming substrate in the above ink-jet printing head by enlarging
the vicinity of an ink supply port, a pressure generating chamber and a nozzle communicating
hole and Fig. 3 is a perspective drawing showing the vicinity of a reservoir, the
ink supply port, the pressure generating chamber and the nozzle communicating hole
in the flow passage forming substrate of the above ink-jet printing head by enlarging
the above vicinity;
Figs. 4, 5 and 6 respectively show an embodiment in case the flow passage forming
substrate according to the present invention is manufactured by anisotropic etching
using a monocrystalline silicon substrate;
Figs. 7 (a) and 7 (b) show another embodiment of the ink-jet printing head according
to the present invention as the sectional structure viewed along a center line between
adjacent pressure generating chambers;
Figs. 8 (a) and 8 (b) show further another embodiment of the ink-jet printing head
according to the present invention as the sectional structure viewed along a center
line between adjacent pressure generating chambers;
Fig. 9 is a top view showing the arrangement of nozzle apertures which may be applied
to the ink-jet printing head shown in Figs. 8 in relationship between the arrangement
of nozzle apertures and the flow passage forming substrate;
Figs. 10 (a) and 10 (b) each shows the other embodiment of the ink-jet printing head
according to the present invention as the sectional structure viewed along a center
line between adjacent pressure generating chambers;
Fig. 11 is a top view showing another embodiment of the flow passage forming substrate
used for the ink-jet printing head according to the present invention;
Fig. 12 is a top view showing the other embodiment of the flow passage forming substrate
used for the ink-jet printing head according to the present invention;
Fig. 13 shows an example of a conventional type ink-jet printing head and Fig. 14
is a perspective drawing showing an example of a flow passage forming substrate in
the conventional type ink-jet printing head.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] The present invention will be described in detail based upon embodiments shown in
the drawings below.
[0013] Figs. 1 (a) and 1 (b) show an embodiment of the present invention as the sectional
structure viewed along a center line (a line A-A and a line B-B in Fig. 2) between
adjacent pressure generating chambers 2, a flow passage forming substrate 1 is made
of a monocrystalline silicon substrate in this embodiment, a pressure generating chamber
2 is formed by anisotropic half-etching as a shallow concave portion, and a first
reservoir 3 and a second reservoir 4 are also formed by anisotropic etching in two
columns as a through hole in this embodiment on both sides of each pressure generating
chamber 2. Each pressure generating chamber 2 adjacent in a row communicates with
the first reservoir 3 or the second reservoir 4 via an ink supply port 5 or 6 which
is a concave portion with depth approximately equal to the depth of the pressure generating
chamber 2.
[0014] At the end on the side on which the ink supply port 5 or 6 is not formed, a nozzle
communicating hole 7 or 8 pierced from the pressure generating chamber 2 to the other
surface, that is, to the surface of a nozzle plate 13 is formed. In Fig. 2, zigzag
hatching shows an area which is not etched, oblique hatching shows a half-etched area
and further, an area which is not hatched shows a through hole.
[0015] The surface on the side of the pressure generating chamber of the spacer 1 constituted
as described above is sealed by an elastic plate 10, the other surface is sealed by
a nozzle plate 13 in which a nozzle aperture 11 or 12 is made in an area opposite
to each nozzle communicating hole 7 or 8 and a flow passage unit is composed of the
above members.
[0016] In each pressure generating chamber 2, pressure generating means, a piezoelectric
vibrator 14 in a longitudinal vibration mode which is pressure generating means in
the present embodiment is provided in an approximately central area on the center
line A-A or B-B between the pressure generating chambers 2 on the elastic plate 10
with the end of the piezoelectric vibrator in contact with an island part 10a formed
on the elastic plate 10 and with the other end fixed to a head frame not shown which
also functions as a fixing member. The piezoelectric vibrators 14 which respectively
function as pressure generating means are arranged by the number of the pressure generating
chambers 2 in the row of the pressure generating chambers 2.
[0017] In this embodiment, when a driving signal is applied to the piezoelectric vibrator
14, the piezoelectric vibrator 14 is contracted and the pressure generating chamber
2 is expanded. Ink in the first or second reservoir 3 or 4 flows into the pressure
generating chamber 2 via the ink supply port 5 or 6 because of the above expansion.
[0018] Next, when the charges of the piezoelectric vibrator 14 are discharged, the piezoelectric
vibrator 14 expands to an original state and compresses the pressure generating chamber
2. Hereby, pressurized ink is jetted as an ink droplet from the nozzle aperture 11
or 12 via the nozzle communicating hole 7 or 8.
[0019] In this embodiment, as the nozzle communicating holes 7 and 8 of adjacent pressure
generating chambers 2 are arranged at least at an interval L shown in Fig. 2 in the
longitudinal direction of the pressure generating chamber 2 and the height M of areas
15' and 15'' respectively opposite to the nozzle communicating holes 7 and 8 of a
partition 15 for partitioning adjacent pressure generating chambers 2 as shown in
Fig. 3 is equal to the depth N of each pressure generating chamber 2 and shallow,
the areas 15' and 15'' are provided with sufficient rigidity approximately equal to
the rigidity of the partition 15 partitioning adjacent pressure generating chambers
2. Therefore, the areas 15' and 15'' adjacent to each nozzle communicating hole 7
or 8 of the partition 15 are never deformed by pressure when ink is jetted and crosstalk
is prevented.
[0020] As the nozzle apertures 11 and 12 which respectively communicate with adjacent pressure
generating chambers 2 can be arranged at an interval in the longitudinal direction
of the pressure generating chamber 2, the degree of freedom is enhanced in the layout
of nozzle apertures and distortion when the nozzle plate 13 is pressed can be dispersed.
[0021] Figs. 4 to 6 show a method of manufacturing the above flow passage forming substrate,
taking a case that one reservoir and one nozzle communicating hole are formed as an
example and a silicon oxide film 22 which functions as a film for protecting from
etching is formed on the whole surface of a monocrystalline silicon substrate 21 with
thickness easy to handle, for example the thickness of approximately 500 µm and the
orientation of a crystal plane of (110) by thermal oxidation so that the silicon oxide
film has predetermined thickness, for example, is 1 µm thick. As for the film for
protecting from etching, if a substance provided with corrosion resistance to anisotropic
etchant is formed as a film such as a silicon nitride film and a metallic film as
shown in Fig. 4 (I), the similar action as a film for protecting from etching is produced.
[0022] Next, a photoresist is applied uniformly on both surfaces of the silicon oxide film
22 by spinning and others to form photoresist layers 23 and 24 as shown in Fig. 4
(II) and resist patterns 25, 25', 26 and 26' to be the pressure generating chamber
2 and the reservoir 3 are formed on both sides by photolithography as shown in Fig.
4 (III).
[0023] Patterns 27, 27', 28 and 28' respectively corresponding to the resist patterns 25,
25', 26 and 26' are transferred as a result of half-etching the silicon oxide film
22 by dipping the monocrystalline silicon substrate 21 in buffer hydrofluoric solution
as shown in Fig. 4 (IV).
[0024] Next, a pattern 29 for an ink supply port is formed on one surface by exposing and
developing areas to be the ink supply ports 5 and 6 and the pressure generating chamber
2 as shown in Fig. 5 (I) and the monocrystalline silicon substrate 21 is etched by
dipping the monocrystalline silicon substrate in buffer hydrofluoric solution again
until the patterns 27, 27', 28 and 28' of the silicon oxide film formed in the above
process shown in Fig. 4 (IV) disappear as shown in Fig. 5 (II). Hereby, a pattern
30 of the silicon oxide film is left and patterns 31, 31', 32 and 32' for anisotropic
etching respectively corresponding to the pressure generating chambers 2 and the reservoirs
3 and 4 are formed on both sides.
[0025] After unnecessary photoresist layers 33 and 34 are peeled as shown in Fig. 5 (III),
an etching pilot hole 33 with depth to the extent that etching can reach the other
surface from one surface of the patterns 31 and 31' to be the approximately parallelogrammatic
pressure generating chamber 2 is made desirably in the center of the pattern 31 by
irradiating a laser beam with wavelength suitable for boring the monocrystalline silicon
substrate 21, for example a YAG laser beam as shown in Fig. 5 (IV).
[0026] When boring operation is finished, the monocrystalline silicon substrate 21 is dipped
in the aqueous solution of potassium hydroxide (KOH) of 20 percent by weight kept
approximately 80°C for anisotropic etching. A reservoir 35 is formed by a monocrystalline
silicon plane (111) with an angle θ to the surface of the monocrystalline silicon
substrate 21 by the above anisotropic etching.
[0027] An area in which the patterns 31 and 31' for the nozzle communicating holes 7 and
8 are formed is etched in the range of the patterns 31 and 31' in the direction of
the thickness, being guided by the etching pilot hole 33 and finally, a through hole
with predetermined cross section is formed as shown in Fig. 6 (I).
[0028] Next, after concave patterns 36 and 37 to be the ink supply ports 5 and 6 and the
pressure generating chamber 2 are formed as shown in Fig. 6 (II), anisotropic etching
is executed as shown in Fig. 6 (III) until the above patterns become concave portions
38 and 39 with depth suitable for the ink supply ports 5 and 6 and the pressure generating
chamber 2 and finally, when the silicon oxide film 22 is removed by etching, a flow
passage forming substrate is completed as shown in Fig. 6 (IV).
[0029] In the above embodiment, the ink supply ports 5 and 6 are formed only on the side
of the elastic plate 10, however, when a second ink supply port 40 or 41 and a second
pressure generating chamber 42 or 43 communicating with the above ink supply port
40 or 41 and the nozzle communicating hole 7 or 8 is formed on the side of the nozzle
plate 13 as shown in Figs. 7 (a) and 7 (b), ink in the reservoir 3 or 4 can be supplied
to the pressure generating chamber 2 via the two ink supply ports 5 and 40 or 6 and
41. Hereby, time required for supplying ink to the pressure generating chamber 2 is
reduced and the printing head can be driven at high speed.
[0030] According to this embodiment, as shown in Figs. 8 (a) and 8 (b), not only the nozzle
aperture 11 or 12 is formed in a position opposite to the nozzle communicating hole
7 or 8 but a nozzle aperture 11' or 11'' is formed in an area opposite to the second
pressure generating chamber 42 or 43 and ink pressurized in the pressure generating
chamber 2 can be jetted as an ink droplet.
[0031] Hereby, if each pressure generating chamber 2 is alternately arranged in a different
direction as shown in Fig. 9, the nozzle apertures 11' and 12' can be also arranged
on the same line Lr and timing when an ink droplet is jetted can be simplified.
[0032] In the above embodiment, the ink supply port 5 or 6 is formed with the width at the
end of the pressure generating chamber 2 narrowed, however, as shown in Fig. 9, a
part not etched 44 or 45 may be also provided on the side of the reservoir in the
pressure generating chamber 2 to adjust resistance in a passage.
[0033] Also, in the above embodiment, the ink supply port 5 or 6 is formed at one end on
the side apart from the nozzle aperture 11 or 12 in the pressure generating chamber
2 and ink is supplied from one side, however, first and second ink supply ports 5
and 46 or 6 and 47 may be also formed on both sides of each pressure generating chamber
2 as shown in Figs. 10 so that the two ink supply ports respectively communicate with
the two reservoirs 3 and 4 arranged with the pressure generating chamber 2 between
the two reservoirs.
[0034] Further, in the above embodiment, the nozzle communicating hole 7 and the pressure
generating chamber 2 are formed so that they have the same width, however, even if
a nozzle communicating hole 48 or 49 with width Wb narrower than the width Wa of the
pressure generating chamber 2 is formed as shown in Fig. 11, the similar action is
produced. In Fig. 11, zigzag hatching shows an area which is not etched, oblique hatching
shows a half-etched area and further, an area which is not hatched shows a through
hole.
[0035] Furthermore, in the above embodiment, the width of the pressure generating chambers
2 alternately arranged in a reverse direction is equalized, however, as ink droplet
jetting performance can be changed by making a difference between the width Wc and
Wd of the pressure generating chambers 2 different in a direction as shown in Fig.
12, the width suitable for the viscosity and property of ink can be selected, each
ink droplet of different types of ink in one printing head, for example each ink droplet
of black ink and color ink or each ink droplet of different colors of ink can be adjusted
in size suitable for printing and the degree of freedom of usable ink can be enhanced.
[0036] In the above embodiment, the flow passage forming substrate is processed by anisotropically
etching a monocrystalline silicon substrate in which a concave portion and a through
hole can be formed precisely, however, as it is clear that the strength of the partition
in the vicinity of the nozzle communicating hole can be also enhanced if the flow
passage forming substrate is formed by boring a thin plate made of metal, ceramics
or glass or by the injection molding of polymeric material, the similar action is
also produced in case the flow passage forming substrate is formed by material except
a monocrystalline silicon substrate.
[0037] As described above, as in an ink-jet printing head according to the present invention,
the two reservoirs are formed with the pressure generating chamber between them, the
pressure generating chamber communicates with at least one reservoir via the ink supply
port and adjacent nozzle communicating holes are arranged in approximately opposite
positions with the center in the longitudinal direction of the pressure generating
chamber between the adjacent nozzle communicating holes and arranged zigzag with the
adjacent nozzle communicating holes shifted in the longitudinal direction of the pressure
generating chamber, the height of the partition for partitioning the nozzle communicating
hole which is a through hole and the adjacent pressure generating chamber is approximately
equal to the height of the partition between the adjacent pressure generating chambers
and rigidity enough to prevent crosstalk can be kept.
[0038] As the nozzle apertures can be arranged in different positions in the longitudinal
direction of the pressure generating chamber, the degree of freedom of the position
of the nozzle aperture is high and distortion when the nozzle plate is added can be
dispersed.
1. An ink-jet printing head comprising a flow passage forming substrate made of a plate
in which a pressure generating chamber, a reservoir, an ink supply port and a nozzle
communicating hole which is a through hole are formed, a nozzle plate provided with
a nozzle communicating with said pressure generating chamber via said nozzle communicating
hole, a capping member for sealing the side of said pressure generating chamber of
said flow passage forming substrate and pressure generating means for pressurizing
said pressure generating chamber, wherein:
two reservoirs are formed with said pressure generating chamber between said two reservoirs;
said pressure generating chamber communicates with at least one reservoir via said
ink supply port; and
adjacent said nozzle communicating holes are arranged in approximately opposite positions
with the center in the longitudinal direction of said pressure generating chamber
between said adjacent nozzle communicating holes and arranged zigzag with said adjacent
nozzle communicating holes shifted in the longitudinal direction of said pressure
generating chamber.
2. An ink-jet printing head according to Claim 1, wherein: said ink supply port is formed
on the side on which said pressure generating chamber is formed.
3. An ink-jet printing head according to Claim 1, wherein: said ink supply ports are
formed on the sides of said capping member and said nozzle plate.
4. An ink-jet printing head according to Claim 1, wherein: said ink supply ports are
formed at both ends of said pressure generating chamber.
5. An ink-jet printing head according to Claim 1, wherein: said nozzle communicating
hole is formed so that the width is narrower than the width of said pressure generating
chamber.
6. An ink-jet printing head according to Claim 1, wherein: said nozzle communicating
hole is formed by being etched from a hole with a minute diameter.
7. An ink-jet printing head according to Claim 1, wherein: said pressure generating means
is constituted by a piezoelectric vibrator; said pressure generating means is extended
in the direction of the row of said pressure generating chambers; and said pressure
generating means is arranged on the approximately center line of said pressure generating
chamber.
8. An ink-jet printing head according to Claim 1, wherein: the width of adjacent said
pressure generating chambers is different.
9. An ink-jet printing head according to Claim 1, wherein: a second ink supply port is
also provided on the side of said nozzle plate; and a passage from said second ink
supply port to said nozzle communicating hole is provided.
10. An ink-jet printing head according to Claim 9, wherein: said nozzle aperture is formed
in a position opposite to said passage.
11. An ink-jet printing head according to Claim 9, wherein: said nozzle apertures are
arranged approximately straight.
12. An ink-jet printing head according to Claim 1, wherein: said flow passage forming
substrate is constituted by anisotropically etching a monocrystalline silicon substrate.